Understanding of neuromuscular disease is founded on careful clinical observation, electrodiagnostic studies and pathology. This protocol has been carried out to learn more about established diseases, to characterize new disease, to assess current methodologies and technologies and technologies and to refine old methods and develop new ones. We have started a study of patients with Charcot-Marie-Tooth disease, with the object of discovering whether the affected peripheral nerve fibers are more severely damaged in their distal parts (near the muscles) or in their proximal parts (near the spinal cord). This information should help us to understand the nature of the underlying pathological defect. We also set up study of the refractory period of transmission in pathological nerve fibers at entrapment sites, using carpal tunnel syndrome patients as subjects. This enable us to assess the severity of entrapment by criteria different from those used in conventional conduction studies. We are continuing to study patients who have previously had poliomyelitis and who notice increasing weakness many years after the acute attack. While these patients show abnormalities of their surviving motor units, such changes are difficult to quantitate; nor is it clear whether or not the number of surviving motor units gradually decreases in such patients. We have set up a study of refractory period in the surviving motor axons of ALS patients as there is some evidence that this becomes increasingly abnormal in any one axon as it approaches the muscle. There are considerable technical problems in recording the refractionary period of single motor axons in man, which we are slowly surmounting.